As shown in, e.g., FIG. 6, a conventional probe apparatus includes: an apparatus main body 1; a mounting table 2 provided in the apparatus main body 1 to mount thereon an object to be tested (e.g., a semiconductor wafer) W, the mounting table 2 being movable in X, Y, Z and θ direction; a probe card 3 having a plurality of probes 3A to be brought into contact with electrode pads of a plurality of devices formed on the semiconductor wafer W mounted on the mounting table 2; a fixing mechanism 4 for fixing the probe card 3 via a card holder (not shown); and a connection ring 5 for electrically connecting the probe card 3 and a test head T. This conventional probe apparatus is configured to test electrical characteristics of each device by transmitting and receiving test signals between a tester (not shown) and the electrode pads of each device formed on the semiconductor wafer W via the test head T, the connection ring 5 and the probe card 3. Moreover, in FIG. 6, a reference numeral ‘6’ indicates a mechanism for position-aligning the semiconductor wafer W and the probe card 3 in cooperation with the mounting table 2; a reference numeral ‘6A’ represents an upper camera; a reference numeral ‘6B’ denotes a lower camera; and a reference numeral ‘7’ indicates a head plate to which the fixing mechanism 4 of the probe card 3 is attached.
In order to test the semiconductor wafer W, tip positions of the probes 3A are detected by the lower camera 6B of the alignment mechanism 6, and positions of the electrode pads of the wafer W which correspond to the probes 3A of the probe card 3 are detected by the upper camera 6A. Next, the alignment between the semiconductor wafer W and the probe card 3 is performed and, then, the mounting table 2 is raised to bring the semiconductor wafer W and the probes 3A into contact with each other. Thereafter, the semiconductor wafer W and the probes 3A are brought into electrical contact with each other by overdriving the mounting table 2, and the test of the semiconductor wafer W is carried out.
Although the probe card 3 is electrically connected with the test head T via the connection ring 5, the probe card 3 is lowered due to a load of the test head T and, hence, a central portion of the head plate 7 which forms an interface mechanism with respect to the tester is slightly deformed, as illustrated in FIG. 7A.
Further, during the test of the semiconductor wafer W, the alignment between the electrode pads of the semiconductor wafer W and the probes 3A corresponding thereto is performed by the alignment mechanism 6 and, then, the mounting table 2 is raised to bring the semiconductor wafer W into contact with the probe card 3. Further, the semiconductor wafer W and the probes 3A are brought into electrical contact with each other by overdriving the mounting table 2. At this time, the probe card 3 is slightly raised by the mounting table 2 and, accordingly, the central portion of the head plate 7 is deformed upward, as depicted in FIG. 7B.
By overdriving the mounting table 2, the head plate 7 is deformed from a position shown in a left half side of FIG. 7C to a position shown in a right half side of FIG. 7C. As a consequence, the probe card 3 is displaced upward by, e.g., about 10 to 20% of the overdriving amount. For that reason, an originally intended overdriving amount (e.g., about 100 μm) may not be accurately applied to the mounting table 2 and, also, a good electrical contact state may not be guaranteed, which may deteriorate the reliability of the test. Especially, when test is performed in a state where the probes 3A of the probe card 3 are required to be brought into contact with respectively corresponding devices of the semiconductor wafer W all at once, the deformation of the head plate 7 can affect the test greatly.
As for a technique related to an overdriving, there are suggested techniques disclosed in, e.g., Patent Documents 1 to 4. In the technique of Patent Document 1, there is provided an optical length-measuring unit for measuring vertical displacement of a probe card. A lifting amount of a mounting table is adjusted based on a displacement of the probe card obtained by the optical length-measuring unit, and the semiconductor wafer and the probe card are brought into contact with each other by a proper overdriving amount. In the technique of Patent Document 2, an overdriving amount of a mounting table can be appropriately set by accurately detecting displacement of a probe card deformed by overdriving the mounting table. Further, in the technique of Patent Document 3, an overdriving amount of a mounting table is controlled based on a result obtained by measuring a height of a thermally deformed probe card by a sensor. All of these techniques attempt to obtain a proper overdriving amount by considering influence of the deformation of the probe card or the lowering of the mounting table, but cannot cope with the case where the interface mechanism including the probe card or the head plate is deformed during the test. Furthermore, in a technique of Patent Document 4, a predetermined overdriving amount is obtained by bringing a stopper provided at a mounting table into contact with a probe card. However, in this technique, a weight of the mounting table may increase.    [Patent Document 1] Japanese Patent Laid-open Publication No. 2004-265895    [Patent Document 2] Japanese Patent Laid-open Publication No. 2003-050271    [Patent Document 3] Japanese Patent Laid-open Publication No. 2003-168707    [Patent Document 4] Japanese Patent Laid-open Publication No. 2005-049254